To make DICOM devices and non-DICOM devices compatible, we need to convert the file format from one to the other. The characteristics of DICOM image file format and normal image file format are studied. The two kinds of file information are construcated, and the file format conversion is implemented. The authors develop a software to convert the file formats between DICOM files and Non-DICOM files. It has been successfully used in PACS, which are operating at hospitals, such as Hospital of anhui province. It is shown that the file format conversion can be implements and can not lose information, and can meet the basic need.